fsm2 3.2.1

FSM2 provides an implementation of the core design aspects of the UML state diagrams allowing both declarative transitions and dynamic transitions along with Guard Conditions.

FSM2 provides an implementation of the core design aspects of the UML2 state diagrams.

FMS2 supports:

• Nested States
• Concurrent Regions
• Guard Conditions
• sideEffects
• onEnter/onExit
• streams
• static analysis tools
• visualisation tools.

Overview

FSM2 uses a builder to delcare each state machine.

Your application may declare as many statemachines as necessary.

Example

import 'package:fsm2/fsm2.dart';

void main() {
  final machine = StateMachine.create((g) => g
    ..initialState(Solid())
    ..state<Solid>((b) => b
      ..on<OnMelted, Liquid>(sideEffect: (e) async => print("I'm melting"))
    ..state<Liquid>((b) {})
 ));

The above examples creates a Finite State Machine (machine) which declares its initial state as being Solid and then declares a single transition which occurs when the event OnMelted event is triggered causing a transition to a new state Liquid.

To trigger an event:

machine.applyEvent(OnMelted());

Documentation

Full documentation is available on gitbooks at:

https://fsm2.onepub.dev/

Example 2

A simple example showing the life cycle of H2O.

import 'package:fsm2/fsm2.dart';

void main() {
  final machine = StateMachine.create((g) => g
    ..initialState(Solid())
    ..state<Solid>((b) => b
      ..on<OnMelted, Liquid>(sideEffect: (e) => print('Melted'),
          )))
    ..state<Liquid>((b) => b
      ..onEnter((s, e) => print('Entering ${s.runtimeType} State'))
      ..onExit((s, e) => print('Exiting ${s.runtimeType} State'))
      ..on<OnFroze, Solid>(sideEffect: (e) => print('Frozen')))
      ..on<OnVaporized, Gas>(sideEffect: (e) => print('Vaporized'))))
    ..state<Gas>((b) => b
      ..on<OnCondensed, Liquid>(sideEffect: (e) => print('Condensed'))))
    ..onTransition((t) => print(
        'Received Event ${t.event.runtimeType} in State ${t.fromState.runtimeType} transitioning to State ${t.toState.runtimeType}')));

  await machine.complete;

  ///   machine.isInState<Hard>()

  print(machine.isInSt<Solid>); // TRUE

  machine.transition(OnMelted());
  print(machine.isInState<Liquid>); // TRUE

  machine.transition(OnFroze());
  print(machine.isInState<Solid>); // TRUE
}

Credits:

FMS2 is derived from the FSM library which in turn was inspired by Tinder StateMachine library.